Journal
MATERIALS & DESIGN
Volume 160, Issue -, Pages 895-905Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.matdes.2018.10.025
Keywords
Invar alloy; Laser powder bed fusion; Porosity; Microstructure; Thermal expansion
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Funding
- Federal Economic Development Agency for Southern Ontario (FedDev Ontario, Canada)
- Burloak Technologies (Ontario, Canada)
- Burloak Technologies
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In the present research, structural analyses are conducted on Invar (64% Fe-36% Ni) samples manufactured by modulated laser powder bed fusion (LPBF) under different laser power regimes. Within the selected process window, the results obtained from X-ray computed tomography analysis indicate that the relative density of as-built samples increases with an increase in laser power. In addition, it is observed that irregular-shaped pores with the longest axis normal to the building direction are significantly reduced with increasing the laser power. Microstructural investigation suggests that with increasing the laser power, a transformation from conduction to transition and keyhole modes occurs. In X-ray diffraction patterns of the as-built samples, only fcc gamma-phase is detected and no reflection of bcc alpha-phase is found. Texture measurements show that the intensity of < 110 > crystallographic orientation along the building direction of the as-built samples increases with increasing laser power. Coefficient of thermal expansion of the as-built samples is very low and comparable to that of conventionally manufactured Invar alloy. Furthermore, as-built samples fabricated at lowest (250 W) and highest (400 W) laser powers exhibit the lowest and highest thermal expansion displacement, respectively. Finally, the thermal expansion behavior and its correlation with structural integrity and texture are discussed. (C) 2018 Elsevier Ltd. All rights reserved.
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